In the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) of a Long Term Evolution (LTE) system of the 3rd generation mobile communication, the data of the uplink are transmitted via a Physical Uplink Shared Channel (PUSCH). An Evolved NodeB (eNB) allocates uplink radio resources to each User Equipment (UE). The access technology adopted in the E-UTRAN is Orthogonal Frequency Division Multiplexing (OFDM) technology, and compared with the 2nd generation mobile communication system, the radio resource management of the E-UTRAN system has the features such as large bandwidth and multiple time processes, and its radio resources are present in two dimensions of time and frequency, so the number of users that can be borne is greatly increased.
The Radio Resource Control (RRC) layer of the LTE system will send a RRC message to implement various operations between the UE and the eNB such as establishment of RRC layer link, configuration of system parameters and transmission of UE capability parameters. Wherein, the RRC message of the downlink is transmitted on a Physical Downlink Shared Channel (PDSCH). Some public parameters related with the system, for example information such as cell frequency point and cell system bandwidth, are sent to all UEs within the cell by the eNB in a broadcast message, and the broadcast message is transmitted on a Physical Broadcast Channel (PBCH).
In order to allocate resources and provide services for each UE according to its requirements so as to realize better multiplexing performance in the uplink transmission and meanwhile in order to utilize the system bandwidth fully, flexibly and highly efficiently, the LTE system formulates a special control message for allocation of uplink transmission resources of the user. Wherein, the control message specially used for allocating resources for the PUSCH is sent by the eNB to the UE, and this resource allocation control message is also called as UpLink Grant (UL Grant), which is transmitted on a Physical Downlink Control Channel (PDCCH).
In order to ensure that radio resources are allocated to each UE reasonably, the LTE system requires that the UE reports the data-amount status of data stored in its buffer, and this report is reported to the eNB in a form of Buffer Status Report (BSR). In the LTE system, the Logical Channels (LCHs) of the UE are divided into four Logical Channel Groups (LCGs) according to the priorities, and the BSR is precisely to report the information of the group number of each LCG and the amount of data to be transmitted of all LCHs in each LCG.
Since BSR is important reference information for the eNB to reasonably perform radio resource scheduling for the UE, many types of BSRs and transmission rules are regulated in the LTE system. According to different events for triggering a BSR, BSR is divided into Regular BSR, Periodic BSR and Padding BSR.
Wherein, the conditions for triggering a regular BSR include:
1, upper-layer transmittable data of a high-priority logical channel arrive, and its priority is higher than that of the existing LCH data in the buffer of the UE;
2, the serving cell changes;
3, the BSR retransmission timer (RETX BSR TIMER) times out, and there are transmittable data in the buffer of the UE.
The condition for triggering a periodic BSR is that: if the periodic BSR timer times out, a periodic BSR is triggered.
The condition for triggering a padding BSR is that: if there is neither regular BSR to be sent nor periodic BSR to be sent, and the number of bits for padding in the allocated uplink PUSCH resources is greater than or equal to the sum of the sizes of the BSR Media Access Control Control Element (MAC CE) and its MAC subheader, then a padding BSR is triggered.
The padding BSR is a padding type BSR, which is supplementation to the regular BSR and the periodic BSR, and correspondingly, the regular BSR and the periodic BSR may be grouped into non-padding type BSRs. When the uplink does not transmit any regular BSR or periodic BSR, a padding BSR allows the eNB to acquire the situation of LCG data change of the buffer of the UE timely.
The regular BSR and the periodic BSR are both encapsulated into a MAC Control Element (CE) in a Media Access Control Protocol Data Unit (MAC PDU). The padding BSR is padded in Padding of the MAC PDU. MAC PDU is transmitted on the PUSCH.
According to the current definition of the protocol standards (3 Gpp TS36.321) of the LTE MAC layer, the aforesaid MAC PDU is as shown in FIG. 1, where one MAC PDU is composed of one MAC header, 0 or more MAC CEs, 0 or more MAC Service Data Units (SDUs) and optional Padding. The MAC header is composed of a plurality of MAC subheaders, each of which corresponds to MAC CE, MAC SDU or Padding aligned after the MAC header in turn according to the sequence of the arrangement
FIGS. 2, 3 and 4 describe the composition structure of the MAC subheader. The LCID contained in the MAC subheader is the type of the corresponding MAC CE or MAC SDU or Padding, for example the explanation of an uplink LCID is as shown in Table 1.
TABLE 1IndexValue of LCID00000CCCH00001-01010Identity of the logical channel01011-11001Reserved11010Power Headroom Report11011Cell radio network tempoary identity (C-RNTI)11100Truncated BSR11101Short BSR11110Long BSR11111Padding
F is the length of the corresponding MAC CE or MAC SDU or Padding, and R is reserved bit.
According to the current definition of the protocol standards (3 Gpp TS36.321) of the LTE MAC layer, Padding BSR can only be transmitted using the Padding of the MAC PDU.
The format of the BSR defined in the LTE system has two types, as shown in FIG. 5 and FIG. 6, where the BSR format shown in FIG. 5 is called as a short BSR format or truncated BSR format, and the BSR format shown in FIG. 6 is called as a long BSR format. BSR is borne by a Physical Uplink Shared Channel (PUSCH). When the UE triggers a BSR, and only one LCG has data to be transmitted, the UE adopts a short BSR format to report BSR; when the BSR triggered by the UE is a Regular BSR or a Periodic BSR, and a plurality of LCGs have data to be transmitted, the UE adopts a long BSR format to report BSR; when the BSR triggered by the UE is a Padding BSR, a plurality of LCGs have data to be transmitted and the bit length of Padding of the MAC PDU is not sufficient to transmit long BSR format, the UE adopts the truncated BSR format to report Padding BSR.
In the above BSR formats, the BSR of a single LCG is indicated by 6 bits, and the value of these 6 bits is used as an index for query in a table of buffer size levels of the BSR. The specific contents of the table are as shown in Table 2.
TABLE 2Buffer Size (BS)Indexvalue [bytes]0BS = 010 < BS <= 10210 < BS <= 12312 < BS <= 14414 < BS <= 17517 < BS <= 19619 < BS <= 22722 < BS <= 26826 < BS <= 31931 < BS <= 361036 < BS <= 421142 < BS <= 491249 < BS <= 571357 < BS <= 671467 < BS <= 781578 < BS <= 911691 < BS <= 10717107 < BS <= 12518125 < BS <= 14619146 < BS <= 17120171 < BS <= 20021200 < BS <= 23422234 < BS <= 27423274 < BS <= 32124321 < BS <= 37625376 < BS <= 44026440 < BS <= 51527515 < BS <= 60328603 < BS <= 70629706 < BS <= 82630826 < BS <= 96731967 < BS <= 1132321132 < BS <= 1326331326 < BS <= 1552341552 < BS <= 1817351817 < BS <= 2127362127 < BS <= 2490372490 < BS <= 2915382915 < BS <= 3413393413 < BS <= 3995403995 < BS <= 4677414677 < BS <= 5476425476 < BS <= 6411436411 < BS <= 7505447505 < BS <= 8787458787 < BS <= 102874610287 < BS <= 120434712043 < BS <= 140994814099 < BS <= 165074916507 < BS <= 193255019325 < BS <= 226245122624 < BS <= 264875226487 < BS <= 310095331009 < BS <= 363045436304 < BS <= 425025542502 < BS <= 497595649759 < BS <= 582555758255 < BS <= 682015868201 < BS <= 798465979846 < BS <= 934796093479 < BS <= 10943961109439 < BS <= 12812562128125 < BS <= 15000063BS > 150000
The above formats of BSR and the definition on the transmission rules are all defined by the current LTE release 8 standard, and in order to adapt to the requirements of various radio services rapidly developing currently and in the future, the next evolved standard of LTE release 8 has also entered a formulating process, that is, the LTE-Advanced standard.
LTE-Advanced is a standard proposed by the 3rd Generation Partner Project (3GPP) organization for meeting the requirements of International Mobile Telecommunication-Advanced (IMT-Advanced) of the International Telecommunication Union (ITU). The LTE-Advanced system is an evolved version on the basis of LTE release 8 system, and it introduces many new techniques to meet the basic requirements of IMT-Advanced, wherein the most important technique is precisely carrier aggregation.
Due to the current lack of radio spectrum resources, the spectrum resources owned by various mobile operators all over the world are very scattered, and the index of peak rate required by IMT-Advanced is even higher (100 Mbps being supported under a high mobility while 1 Gbps being supported under a low mobility). The maximum bandwidth of 20 MHz according to the current LTE standard cannot meet the requirements of IMT-Advanced, so it needs to be extended to a higher bandwidth, for example, Frequency Division Duplexing (FDD) can support 80 MHz at most, Time Division Duplexing (TDD) can support 100 MHz at most, accordingly, the data amount that can be transmitted by the UE is also increased by several times relative to the LTE. In addition to increase of the bandwidth, to achieve an even higher rate, Multiple Input Multiple Output (MIMO) is also a core technique for increasing the throughput of the LTE-A system. Considering both increase of uplink bandwidth (five times of the bandwidth of LTE) and uplink double-stream MIMO (twice of the single-stream of LTE), the uplink rate of the UE in a LTE-A system will be increased to 10 times of that in the LTE system.
However, the original BSR table can only indicate data with a maximum of 150000 in a fine granularity, and all other services larger than 150000 belong to the same BSR level, that is, if the BSR table of LTE is still used, then the LTE-A services of large throughput will cause the network to be unable to distinguish the buffer status from 150000 to 1500000 of the UE, thus making it unable to allocate resources reasonably and efficiently. Therefore, the 3GPP meets the requirement of accurately reflecting the buffer status from 150000 to 1500000 in a case of large service throughput of the LTE-A by adding at least one new BSR table on the basis of BSR table of the LTE. Nevertheless, how to use these tables with the UE supporting a plurality of BSR tables is not determined yet.